The present invention relates to the monitoring and diagnosis of electrical motors, especially motors monitored by sensors located both at the motor and remotely at a circuit breaker or other remote motor control unit.
In one embodiment, the invention is a novel motor "fingerprinting" system that monitors and simultaneously tracks several dynamic and static motor conditions on site at the motor and from a remote motor control center. The data on the static and dynamic motor conditions is synchronized and stored in databases maintained at the motor, the motor control center and/or a central and/or local location. The invention may further include a novel method for determining the torque output of a motor based on the data collected from the motor.
Industrial electrical motors are in widespread use in manufacturing, power generation and other industrial facilities. These motors must be monitored and maintained to ensure their proper operation. There are a wide variety of motor parameters that can be monitored to provide service personnel with information regarding the condition of a motor. These parameters include dynamic operating conditions, such as vibration, speed, temperature, and stray magnetic flux that are measured by sensors on or adjacent the motor. Other dynamic motor parameters, such as voltage and current, are best monitored at remote stations, such as at transformers and circuit breakers where those parameters can be safely monitored by avoiding the high voltage and current levels that may exist directly at the motor. In addition, static motor conditions, such as current leakage through insulation, are measured when the motor is off-line, e.g., disconnected from its power supply.
In the past, static and dynamic motor parameters have not been monitored by an integrated sensor and instrumentation system. Similarly, the data on motor condition has not been collected simultaneously in real-time to allow for review of motor condition data, or to allow for storage of data on various motor parameters in a comprehensive database. Instead of having a synchronized collection of the current and historical data on the condition of a motor, service personnel have had to rely on many independent test instruments and databases to obtain static and dynamic motor data. These independent tests do not collect data synchronously and do not allow service personnel to synchronize data from various test instruments. In addition, the coordinated analysis of certain system events, i.e. contact closures, in conjunction with motor parameters has been difficult if not impossible to achieve. Thus, service personnel are not able to compare the timing of certain test results, such as current and voltage inputs of a motor, with the timing of other test results, such as vibration, stray magnetic flux and motor temperature or system events (i.e., contact closures, valve functions, etc). Other disadvantages of using independent instruments include the inconvenience to service personnel and that service personnel do not have ready access to complete and coordinated motor data when diagnosing motor problems. The motor service personnel have a long-felt need for access to aggregate collections of data on a motor to allow them to better detect when motors require servicing, repairs, or replacement, as well as to assess the suitability of a motor for a certain function or location.
Prior motor test equipment provided limited functional test capability. These prior test instruments were usually individual instruments that addressed a specific motor characteristic or condition. The instruments were also often limited to use with a certain class of motors, such as low voltage, medium voltage, alternating current (AC) induction, AC synchronous, direct current (DC) and other motor classes. A service person had to operate and interpret many different motor test instruments to service motors of different classes. He had to be trained and be knowledgeable of all of the instrument types. The service person also had to have access to each of these instruments, and know where the instruments were positioned with respect to the motor in order to gather the motor data from the instruments.